An electronic material used for electronic components such as liquid crystal display elements and semiconductor elements are required to have excellent visible light permeability and properties such as heat resistance, chemical resistance, and crack resistance, with which an electronic material can tolerate various treatment steps during production of such elements. Silicone polymers have been gaining attention because they have properties such as excellent visible light permeability and heat resistance.
A silicone polymer can be synthesized by conducting a hydrolysis-condensation reaction of a hydrolyzable silicon compound in the presence of a base and then removing a solvent or a by-product by, for example, concentration or the like. In a hydrolysis reaction, a hydrolyzable substituent bound to a silicon atom is hydrolyzed, which results in formation of a silanol group. A condensation reaction between this silanol group and another silanol group or an unreacted hydrolyzable group further takes place, which results in formation of a siloxane bond. This reaction is repeatedly induced. Thus, a silicone polymer is formed. In the condensation reaction, not every silanol group is consumed, and there are some silanol groups remaining after the reaction. When such highly reactive silanol groups remain, silanol groups react by condensation reaction during high-temperature concentration. Accordingly, the molecular weight of a silicone polymer increases compared to silicone before concentration. Therefore, it has so far been impossible to obtain a silicone polymer having desired properties.
Various studies have been made to improve stability of a composition containing such silicone polymer. For example, a process comprising adding an acid to a composition containing a silicone polymer such that the acid content is 0.1 parts by weight with respect to 100 parts by weight of the silicone polymer is disclosed (Japanese Unexamined Patent Publication (Kokai) No. 2010-112966 A). However, in that process, an acid added in a large amount causes deterioration of properties of a silicone polymer upon production of an element. In addition, since an acid is added after production of a silicone polymer in such process, a silicone polymer is denatured during concentration that is carried out at a high temperature upon production of a silicone polymer, making it impossible to obtain a silicone polymer of interest.
There has been a demand for a process of producing a silicone polymer, that does not influence properties of a silicone polymer upon production of an element, and by which it is possible to inhibit an increase in the molecular weight of a silicone polymer during concentration in the steps of producing a silicone polymer.
It could therefore be helpful to provide a process that makes it possible to inhibit an increase in the molecular weight of a silicone polymer during high-temperature concentration in the steps of producing a silicone polymer.